A TIG welding method and plasma welding method have conventionally been used as a non-consumable electrode-type welding method for welding a base material. Since the plasma welding method has superior heat-concentration compared to the TIG welding method, the plasma welding method enables high-speed welding with a narrow bead width and little distortion.
A plasma welding method includes a plasma arc-type (transferred plasma), a plasma jet-type (non-transferred plasma), and the like.
In general, plasma arc type welding apparatus (plasma arc type welding machine) includes a torch, a main power supply in which a negative terminal connects to an electrode constituting the torch and a positive terminal electrically connects with a material to be welded, a pilot arc power supply which is electrically connected to the power supply through a wire, a changing-over switch provided in a wire connecting the pilot arc power supply and an insert chip (may also be referred to as “restraint nozzle”) constituting the torch, and a high-frequency device generating a pilot arc.
By using the plasma arc-type plasma welding apparatus, it is possible to perform high penetration welding.
In a plasma jet-type plasma welding apparatus (plasma jet-type plasma welding machine), an electrode constituting a torch is connected to a negative terminal of a main power supply, and a positive terminal of the main power supply and an insert chip constituting the torch are connected via the positive electrode.
In the plasma jet-type welding apparatus, since an electrical current does not flow through the material to be welded, it can be used as a heat source for thermal-spraying or a heat source for a furnace.
The combined-type plasma welding apparatus disclosed in Patent Document 1 includes a torch and a power supply device (hereinafter, may be referred to as “plasma power source device for a combined-type”). A combined-type plasma power supply device constitutes a main arc power supply (may be referred to as “main power supply”), a pilot arc power supply, and a high-frequency device.
In the main arc power supply (main power supply), the negative terminal is connected with the electrode constituting the torch, and the positive terminal is electrically connected with the material to be welded.
The combined-type plasma welding apparatus having the above-described constitution makes it possible to obtain a stable plasma even with a very low electrical current, thereby allowing welding of a hyper-thin plate, which is difficult to weld by the TIG welding method.